The study, published in The Journal of Clinical Sleep Medicine, found that about 37 percent of the firefighters screened positive for at least one sleep disorder, most for obstructive sleep apnea.

After controlling for sex, race, body mass index, smoking and other factors, the researchers found that compared with sound sleepers, those with a sleep disorder were about twice as likely to have a motor vehicle crash, to nod off while driving, and to have cardiovascular disease or diabetes. They were more than three times as likely to suffer from depression and anxiety.

The investigators acknowledge that some of their data depended on self-reports, which are not always reliable. Still, the lead author, Laura K. Barger, an associate physiologist at Brigham and Women’s Hospital in Boston, said that screening for sleep disorders is important. “If you can get these people evaluated and treated when necessary,” she said, “you can improve the health of workers.”